It’s all relative at the edge of physics

WE ALL know Albert Einstein, don’t we?

Yes, that old guy with the wild hair, the stock image for every lazy and unimaginative advertising executive whenever a mad genius is required. In reality, the Albert Einstein who developed the special theory of relativity in 1905 was a rather conservative-looking young man, a world away from that eccentric stereotype. And he wasn’t standing in front of a blackboard full of equations, explaining his theories to a rapt audience. He was living out a somewhat mundane existence as a clerk in the patent office in Bern.

We are also aware of Einstein’s most famous equation – E=mc².

Do we understand this equation? Do we know where it comes from? Do we realise its consequences?

The answer, for the vast majority of the world’s population, is in the negative. In their book, Why Does E=mc² (and why should we care?), Brian Cox and Jeff Forshaw attempt to provide the answers, using the bare minimum of mathematics.

At the end of the 19th century, physicists declared, with more than a whiff of arrogance, that all there was to know in physics was already known, except for a few niggling loose ends. Einstein picked at those loose ends and, in the process, brought the whole edifice tumbling down.

Victorian physics is often characterised in terms of wooden benches with wires, magnets, jars, lenses and so on. The 21st century version often involves teams of physicists collaborating on enormous projects and hustling for the correspondingly enormous funds required. In contrast, Einstein’s laboratory was his open-ended imagination, where he conducted the thought experiments which led him to his theories.

“If at first an idea does not sound absurd,” he once said, “then there is no hope for it.” At the turn of the 20th century, Isaac Newton’s grand description of “how the world works” had held sway for over 200 years. Indeed, it still works perfectly well at what we consider to be ‘normal’ speeds.

However, Einstein imagined what it would be like to travel at extremely high speeds, both from the viewpoint of the traveller and from that of a ‘stationary’ observer. And he discovered that space and time are not what they seem.

As we approach the speed of light, the cosmic speed limit, the conventional laws of physics – and, along with them, our perceptions of time and space – undergo radical change.

Newton’s theories were assimilated into mankind’s collective consciousness within a relatively short time.

In contrast, more than a century after the publication of his special theory of relativity (the general theory wasn’t published until 1915), Einstein’s ideas remain vaguely understood, despite their critical importance in understanding the structure of the universe.

He was aware of this fact when he stated: “Why is it that nobody understands me and everybody likes me?”

Cox and Forshaw demand no more than a minimal knowledge of mathematics from the reader. If you can handle Pythagoras, you can handle this. However, the authors do demand perseverance and imagination. They warn throughout that so-called common sense is a poor guide.

They chip away at our conventional notions of three-dimensional space and of time that ticks along at a constant rate.

These old ideas have burrowed into our minds over the centuries and therefore constitute significant road blocks on the journey to an understanding of relativity. However, by the time we arrive at the key concept of spacetime, this foundation work pays off handsomely, and we accept readily that time is not constant.

Cox and Forshaw write with style and enthusiasm, and straddle that fine line between patronising us, the readers, with simplicity and losing us in a web of complexity. They lead us sure-footedly through the development of modern physics and into the fascinating world of elementary particles, the very building blocks of the universe. They do so in a manner that is accessible, only occasionally difficult and, very rarely, impenetrable.

Einstein once said: “Make everything as simple as possible, but not simpler.” Cox and Forshaw have followed his advice.